Unlike IPv4, in IPv6, one interface or each of a plurality of interfaces may have multiple IPv6 addresses. Also, a plurality of destination IPv6 addresses included in a Domain Name System (DNS) name query response message may be provided.
Unlike an IPv4 address system, since there exist a plurality of transmission IPv6 addresses at one node, and a plurality of destination IPv6 addresses at one node, there exist a problem of having to select a suitable transmission IPv6 address and a suitable destination IPv6 address for communication between a transmission node and a destination node.
To address this problem, Internet Engineering Task Force (IETF) suggests a transmission and destination address selection algorithm through a document Request For Comments (RFC) 3484.
The transmission and destination address selection algorithm of RFC 3484 uses following information in order to determine a couple of a transmission address and a destination address when there exit a plurality of transmission addresses and destination addresses.
First, an address range is classified into link-local, site-local, and global. An address state is classified into deprecated or not, and reachable or not. An address use purpose is classified into temporary or not. As an address prefix, a longest matching prefix is preferentially selected.
A high address precedence is preferentially selected. Regarding a label value, an address having the same label value is preferentially selected.
FIG. 1 illustrates a communication structure in a general IPv6 network.
Referring to FIG. 1, a transmission host 110 has following addresses.
LAN interface of transmission host3ffe:ffff:21a5:a454:2aa:ff:fe21:5c2f(global address, non-deprecated state, public use)3ffe:ffff:21a5:a454:20da:3198:2c50:1a57(global address, non-deprecated state, temporary use)3ffe:ffff:21a5:a454:1d15:9c:8e4c:902b(global address, deprecated state, temporary use)fec0:3a4f:78ea:a454:2aa:ff:fe21:5c2f (site-local address, non-deprecated state)fe80::2aa:ff:fe21:5c2f(link-local address, non-deprecated state)157.60.17.211 (public IPv4 address [global scope]. non-deprecated state)Automatic tunneling pseudo-interface3ffe:ffff:21a5:a499::5efe:157.60.17.211 (global ISATAP address, non-deprecated state)fe80::5efe:157.60.17.211 (link-local address, non-deprecated state)
In this case, for communication with a destination host 130, the transmission host 110 transmits a “DNS name query request” message to a DNS server 120 in order to determine the address of the destination host 130. The DNS server 120 responds following destination addresses using a “DNS name query response” message.
207.73.118.98 (public IPv4 address [global scope])3ffe:ffff:21a5:a4ca:2aa:ff:fe35:2c1a (global address)3ffe:ffff:21a5:a499::5efe:207.73.118.98 (ISATAP global address)fec0:3a4f:2a34:1aa7:2aa:ff:fe35:2c1a (site-local address)
The transmission and destination address selection algorithm determines a following transmission-destination address couple with respect to the above transmission addresses and destination addresses.
transmission addressdestination addressfec0:3a4f:78ea:a454:2aa:ff:fe21:5c2ffec0:3a4f:2a34:1aa7:2aa:ff:fe35:2c1a3ffe:ffff:21a5:a454:2aa:ff:fe21:5c2f3ffe:ffff:21a5:a4ca:2aa:ff:fe35:2c1a3ffe:ffff:21a5:a499::5efe:157.60.17.2113ffe:ffff:21a5:a499::5efe:207.73.118.98157.60.17.211207.73.118.98
After that, the transmission host 110 and the destination host 130 communicate with each other using the above-determined address couple.
In FIG. 1, in the case where an address couple determined by the transmission and destination address selection algorithm is used, when communication using a first address couple fails, communication may be tried by a frequency of retransmission designated by Transmission Control Protocol (TCP)/User Datagram Protocol (UDP)/Internal Protocol (IP). When all communication fails although communication is tried by the frequency of the retransmission, communication is tried using the next address couple.
However, generally, during an Internet access, when an access fails by a maximum frequency of retransmission, an Internet access failure occurs and an Internet access using the next address couple is not tried.
Also, even though the next address couple may be used when an Internet access using the first address pair fails in FIG. 1, TCP/UDP/IP communication requires a long delay time until the next address couple is used. That is, a delay time as much as the maximum frequency of retransmission using the first address couple occurs.
Therefore, even when there exist useful addresses among transmission addresses not selected by the transmission and destination address selection algorithm, they are not used.
FIG. 2 illustrates an example of an operation of a general transmission and destination address selection algorithm.
Referring to FIG. 2, a host A (210) supports IPv6 and IPv4, and has an IPv6 global address, and an Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) global address which allows an IPv6 address to transition to an IPv4 address via an ISATAP interface. Also, a host B (260) has a global address of IPv6.
A router 230 which connects the host A (210) with the host B (260) has two Network Interface Cards (NICs). An NIC1 supports ISATAP and IPv6, and an NIC2 supports IPv6.
Therefore, an IPv6/IPv4 network 200 may be used as a network between the host A (210) and the NIC1. That is, the host A (210) may transfer a packet to the host B (260) via the IPv6/IPv4 network 200 using an IPv6 address.
Also, the host A (210) may transfer an IPv6 packet encapsulated using IPv4 to the host B (260) by transmitting the IPv6 packet encapsulated using IPv4 through the IPv4 network 200 using the ISATAP interface of the router 230 which uses an IPv6 address.
An exemplary embodiment of the present invention assumes that the host A (210) and the host B (260) have the following address information.
Host A2001:1:2:0:200:f0ff:fe7a:5214 (global address, non-deprecated,public use)2001:DB8:0:7:0:5cfc:192.168.1.10 (global ISATAP address, non-deprecated)Host B2001:3:4:5:1966:b2f1:475c:940c (global address, non-deprecated, public use)
Also, an exemplary embodiment of the present invention assumes that the host B (260) is operated as an Internet Information Service (IIS) server, and the host A (210) is connected to the host B (260) via an Internet web browser. Also, an exemplary embodiment of the present invention assumes that it has been confirmed that all addresses of the host A (210) and the host B (260) are valid addresses as a result of a ping test.
At this point, the address of the host A (210) is determined as “2001:1:2:0:200:f0ff:fe7a:5214” by the transmission and destination address selection algorithm. After that, communication using a transmission address (2001:1:2:0:200:f0ff:fe7a:5214) and a destination address (2001:3:4:5:1966:b2f1:475c:940c) is performed. A communication process is described below.
First, the host A (210) performs a connection to the host B (260). Also, during connection, the router 230 removes an IPv6 function at the NIC1 and leaves only the ISATAP router function. This is for realizing a failure of an IPv6 network.
After that, the host A (210) experiences a connection failure to the host B (260) (connection failure after connection is tried by a frequency of retransmission designated by TCP/UDP/IP).
After that, the host A (210) tries a connection to the host B (260) using the transmission and destination address selection algorithm, but the connection fails because the host A (210) tries a connection by selecting “2001:1:2:0:200:f0ff:fe7a:5214” as a transmission address.
As described in the above example, since “2001:1:2:0:200:f0ff:fe7a:5214” is non-deprecated, “2001:1:2:0:200:f0ff:fe7a:5214” is selected continuously by the transmission and destination address selection algorithm even though a connection fails.
In this case, if an ISATAP address (2001:DB8:0:7:0:5efe:192.168.1.10) were selected during a connection failure, connection would be performed successfully.
Consequently, when the transmission and destination address selection algorithm defined by the document RFC 3484 is used, a long transmission delay time due to a connection failure, and an inefficient address access may be generated.